Frontend module

ABSTRACT

A frontend module includes a first filter having a passband of a first frequency band, a second filter having a passband of a second frequency band, the second frequency band being higher than the first frequency band, a third filter having a passband of a third frequency band, the third frequency band being higher than the second frequency band, and a sub-filter, connected to the second filter, configured to provide attenuation characteristics for the first frequency band, wherein the second filter comprises a plurality of parallel LC resonance circuits arranged between a ground and different nodes, from among a plurality of nodes between a first terminal and a second terminal, wherein an inductor is connected to a portion of the plurality of parallel LC resonance circuits.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC 119(a) of Korean PatentApplication No. 10-2019-0042091 filed on Apr. 10, 2019 and Korean PatentApplication No. 10-2019-0076502 filed on Jun. 26, 2019 in the KoreanIntellectual Property Office, the entire disclosures of which areincorporated herein by reference for all purposes.

BACKGROUND 1. Field

The present disclosure relates to a frontend module.

2. Description of Related Art

Fifth generation (5G) communications are expected to connect moredevices to each other efficiently with larger amounts of data and fasterdata transfer rates, as compared to conventional long-term evolution(LTE) communications.

5G communications are developing in the direction of using a frequencyband of 24,250 MHz to 52,600 MHz, corresponding to a millimeter wave(mmWave) band, and a frequency band of 450 MHz to 6,000 MHz,corresponding to a sub-6 GHz band.

Each of the n77 band (3,300 MHz to 4,200 MHz), the n78 band (3,300 MHzto 3,800 MHz), and the n79 band (4,400 MHz to 5,000 MHz), is defined asone from among the sub-6 GHz operating bands. Also, the n77 band (3,300MHz to 4,200 MHz), the n78 band (3,300 MHz to 3,800 MHz), and the n79band (4,400 MHz to 5,000 MHz) are expected to be used as main bands, dueto the advantages for these bands of having wide bandwidths.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In one general aspect, a frontend module, includes a first filter havinga passband of a first frequency band, a second filter having a passbandof a second frequency band, the second frequency band being higher thanthe first frequency band, a third filter having a passband of a thirdfrequency and, the third frequency band being higher than the secondfrequency band, and a sub-filter, connected to the second filter,configured to provide attenuation characteristics for the firstfrequency band, wherein the second filter includes a plurality ofparallel LC resonance circuits arranged between a ground and differentnodes, from among a plurality of nodes between a first terminal and asecond terminal, wherein an inductor is connected to a portion of theplurality of parallel LC resonance circuits.

The inductor may be configured to provide attenuation characteristicsfor the third frequency band.

The inductor may be disposed between the portion of the plurality ofparallel LC resonance circuits and the ground.

The second filter may include a plurality of inductors, and each of theplurality of inductors may be connected to a different parallel LCresonance circuit of the plurality of parallel LC resonance circuits.

The second filter may include a plurality of capacitors, and each of theplurality of parallel LC resonance circuits may be arranged between aground and a different node between the plurality of capacitors.

The first frequency band may be a band of 3.3 GHz to 4.2 GHz, the secondfrequency band may be a band of 4.4 GHz to 5.0 GHz, and the thirdfrequency band may be a band of 5.15 GHz to 5.95 GHz.

The sub-filter may have a stop band of 4.0 GHz to 4.2 GHz.

The first filter, the second filter, and the third filter may beconnected to an antenna terminal.

In another general aspect, a frontend module includes first filterhaving a passband of a first frequency band, a second filter having apassband of a second frequency band, the second frequency band beinghigher than the first frequency band, a third filter having a passbandof a third frequency band, the third frequency band being higher thanthe second frequency band, and a sub-filter, connected to the secondfilter, configured to provide attenuation characteristics for the firstfrequency band, wherein the second filter includes a plurality of seriesLC resonance circuits arranged between a first terminal and a secondterminal, wherein a capacitor is connected to a portion of the pluralityof series LC resonance circuits.

The capacitor may be configured to provide attenuation characteristicsfor the first frequency band.

The capacitor may be connected to the portion of the plurality of seriesLC resonance circuits in parallel.

The second filter may include a plurality of capacitors, and each of theplurality of capacitors may be connected to a different series LCresonance circuits of the plurality of series LC resonance circuits.

The second filter may include a plurality of inductors, and each of theplurality of series LC resonance circuits may be disposed between theplurality of inductors.

The first frequency band may be a band of 3.3 GHz to 4.2 GHz, the secondfrequency band may be a band of 4.4 GHz to 5.0 GHz, and the thirdfrequency band may be a band of 5.15 GHz to 5.95 GHz.

The sub-filter may have a stop band of 5.15 GHz to 5.35 GHz.

The first filter, the second filter, and the third filter may beconnected to an antenna terminal.

According to another general aspect, a frontend module includes a firstfilter having a passband of a first frequency band, a second filterhaving a passband of a second frequency band, the second frequency bandbeing higher than the first frequency band, a third filter having apassband of a third frequency band, the third frequency band beinghigher than the second frequency band, and a sub-filter, connected tothe second filter, configured to provide attenuation characteristics forthe first frequency band, wherein the second filter includes a pluralityof LC resonance circuits, and a passive element connected to theplurality of LC resonance circuits configured to provide attenuationcharacteristics for the third frequency band.

The LC resonance circuits may be parallel LC resonance circuits and thepassive element may be an inductor.

The LC resonance circuits may be series LC resonance circuits and thepassive element may be a capacitor.

The first filter, the second filter, and the third filter may beconnected to an antenna terminal.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a mobile device on which afrontend module according to an example is mounted.

FIG. 2 illustrates a frequency response of filters required tosimultaneously support a 3.3 GHz to 4.2 GHz band (an n77 band), a 4.4GHz to 5.0 GHz band (an n79 band), and a 5.15 GHz to 5.95 GHz band (a 5GHz Wi-Fi band).

FIG. 3 illustrates a frequency response of a 4.4 GHz to 5.0 GHz band (ann79 band) implemented with a Chebyshev filter.

FIGS. 4A and 4B are block diagrams of frontend modules according tovarious examples.

FIGS. 5A to 5C illustrate a process of deriving a second filteraccording to an example.

FIGS. 6A to 6C illustrate a process of deriving a second filteraccording to an example.

FIG. 7 is a graph illustrating a frequency response of a filter to whicha J-inverter technique or a K-inverter technique is applied.

FIG. 8 illustrates frequency responses by first to third filtersaccording to an example.

FIG. 9 illustrates frequency responses by first to third filters andfirst to third sub-filters according to an example.

FIG. 10 is a block diagram illustrating an example of an amplifierconnected to a filter according to an example.

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements. The drawings may not be to scale,and the relative size, proportions, and depiction of elements in thedrawings may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description of the present disclosure refers tothe accompanying drawings, which illustrate, as an example, specificembodiments in which the present disclosure may be practiced. Theseembodiments may be described in sufficient detail to enable thoseskilled in the art to practice the present disclosure. It should beunderstood that the various embodiments of the present disclosure aredifferent, but do not need to be mutually exclusive. For example,certain shapes, structures, and characteristics described herein may beimplemented in other embodiments without departing from the spirit andscope of the present disclosure in connection with an embodiment. Itshould be also understood that position or arrangement of the individualcomponents within each disclosed embodiment may be varied withoutdeparting from the spirit and scope of the present disclosure. Thefollowing detailed description is, therefore, not to be taken in alimiting sense, and the scope of the present disclosure is limited onlyby the appended claims, along with the full scope of equivalents towhich such claims are entitled, if properly explained. In the drawings,like reference numerals refer to the same or similar functionsthroughout the several views.

Hereinafter, examples will be described in detail with reference to theaccompanying drawings so that those skilled in the art may easily carryout the examples.

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent after an understanding of thedisclosure of this application. For example, the sequences of operationsdescribed herein are merely examples, and are not limited to those setforth herein, but may be changed as will be apparent after anunderstanding of the disclosure of this application, with the exceptionof operations necessarily occurring in a certain order. Also,descriptions of features that are known in the art may be omitted forincreased clarity and conciseness.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided merelyto illustrate some of the many possible ways of implementing themethods, apparatuses, and/or systems described herein that will beapparent after an understanding of the disclosure of this application.

Herein, it is noted that use of the term “may” with respect to anexample or embodiment, e.g., as to what an example or embodiment mayinclude or implement, means that at least one example or embodimentexists where such a feature is included or implemented while allexamples and embodiments are not limited thereto.

An aspect of the present examples is to provide a frontend modulecapable of ensuring sufficient attenuation characteristics forneighboring bands.

FIG. 1 is a block diagram illustrating a mobile device on which afrontend module according to an example is mounted.

Referring to the example of FIG. 1, a mobile device 1 according to anexample may include a plurality of antennas ANT1 to ANT6, and aplurality of frontend modules FEM1 to FEM6, respectively connected todifferent antennas from among the plurality of antennas ANT1 to ANT6.

The mobile device 1 may perform a plurality of standard wirelesscommunications tasks such as cellular (Long-Term Evolution(LTE)/Wideband Code Division Multiply Access (WCDMA)/Global System forMobile (GSM)) communications, Wi-Fi communications of 2.4 GHz and 5 GHzbands, Bluetooth communications, and other similar wirelesscommunications. The plurality of antennas ANT1 to ANT6 and the pluralityof frontend modules FEM1 to FEM6, included in the mobile device, maysupport the plurality of standard wireless communications, such as thosediscussed above.

A Multi-Input/Multi-Output (MIMO) system may be applied for use in themobile device 1. MIMO may be a technique for increasing a bandwidth ofthe mobile device 1 in proportion to the number of antennas. When thenumber N of antennas is used, N times of a frequency efficiency may beobtained, as compared to when using a single antenna. Due to theslimming and miniaturization aspects of mobile devices, there may be alimitation with respect to a space in which the antenna is mounted.There may also be physical limitations in further implementing aplurality of antennas in a terminal under a condition in which theantennas, used in the system according to alternative technologies, areprovided.

Therefore, a frontend module, connected to any one of the antennas, isdesired to be able to support a plurality of standard wirelesscommunications techniques, to be able to reduce the number of antennasmounted on the mobile device 1.

FIG. 2 illustrates a frequency response of filters required tosimultaneously support a 3.3 GHz to 4.2 GHz band (an n77 band), a 4.4GHz to 5.0 GHz band (an n79 band), and a 5.15 GHz to 5.95 GHz band (a 5GHz Wi-Fi band).

In the example of FIG. 2, it is assumed that a first graph, or graph 1,represents a frequency response of filter A supporting the 3.3 GHz to4.2 GHz band (the n77 band), a second graph, or graph 2, represents afrequency response of filter B supporting the 4.4 GHz to 5.0 GHz band(the n79 band), and a third graph, or graph 3, represents a frequencyresponse of filter C supporting the 5.15 GHz to 5.95 GHz band (the 5 GHzWi-Fi band).

The 4.4 GHz to 5.0 GHz band (the n79 band) may have a band gap of 200MHz from the 3.3 GHz to 4.2 GHz band (the n77 band), and a band gap ofonly 150 MHz from the 5.15 GHz to 5.95 GHz band (the 5 GHz Wi-Fi band).

Therefore, the filter A supporting the 3.3 GHz to 4.2 GHz band (the n77band), the filter B supporting the 4.4 GHz to 5.0 GHz band (the n79band), and the filter C supporting the 5.15 GHz to 5.95 GHz band (the 5GHz Wi-Fi band) may have sufficient attenuation characteristics withrespect to each other, such that they may be able to use a method frommethods such as carrier aggregation (CA), LTE in unlicensed spectrum(LTE-U), Licensed Assisted Access (LAA), or another, related method, andsuch a method may be used in one or more of the 3.3 GHz to 4.2 GHz band(the n77 band), the 4.4 GHz to 5.0 GHz band (the n79 band), and the 5.15GHz to 5.95 GHz band (the 5 GHz Wi-Fi band).

Although a Bulk Acoustic Wave (BAW) filter has excellent attenuationcharacteristics, such a BAW filter may not be easily applied toapplications in fifth-generation (5G) communications, requiringbroadband frequency characteristics, because it is difficult to use sucha BAW to form a relatively wide passband. Therefore, in order to satisfythe broadband frequency characteristics required in 5G communications,the filters may be provided as an LC filter, implemented by using acombination of a capacitor and an inductor. Throughout this disclosure,capacitors and inductors are examples of passive elements, along withresistors.

FIG. 3 illustrates a frequency response of a 4.4 GHz to 5.0 GHz band (ann79 band) implemented by using a Chebyshev filter. Such a Chebyshevfilter may be an example of the LC filter, and may correspond to afilter composed of a combination of LC resonators. Chebyshev filtershave the property that they minimize the error between the idealized andthe actual filter characteristic over the range of the filter.

In the example of FIG. 3, a first graph, or graph 1, represents afrequency response of a third order Chebyshev filter, a second graph, orgraph 2, represents a frequency response of a fifth order Chebyshevfilter, a third graph, or graph 3, represents a frequency response of aseventh Chebyshev filter, and a fourth graph, or graph 4, represents afrequency response of a ninth order Chebyshev filter.

Referring to the example of FIG. 3, as the order of the Chebyshev filterincreases, the attenuation characteristics of the Chebyshev filter mayimprove at 4.2 GHz and 5.150 GHz, but insertion loss of the Chebyshevfilter may deteriorate in the 4.4 GHz to 5.0 GHz band (the n79 band).With respect to insertion loss, the fifth order Chebyshev filter may bemore suitable for implementation of the 4.4 GHz to 5.0 GHz band (the n79band). With respect to attenuation characteristics, the ninth orderChebyshev filter may be more suitable for implementation of the 4.4 GHzto 5.0 GHz band (the n79 band). For example, the Chebyshev filtercomposed only of the combination of LC resonators may present an issuethat it does not simultaneously satisfy the pass characteristicsrelevant for the broadband and the attenuation characteristics relevantfor the neighboring bands.

FIGS. 4A and 4B are block diagrams of frontend modules according tovarious examples.

Referring to the example of FIG. 4A, a frontend module according to anexample may include a multiplexer including a first filter F1, a secondfilter F2, and a third filter F3, connected to an antenna terminalT_ANT, and a first sub-filter SF1, a second sub-filter SF2, and a thirdsub-filter SF3. Referring to the example of FIG. 4B, the frontend modulemay be configured to have a form in which the first sub-filter SF1, thesecond sub-filter SF2, and the third sub-filter SF3 are omitted, as analternative example.

Subsequently, for ease of explanation, it is assumed that a frontendmodule according to the present examples includes the first sub-filterSF1, the second sub-filter SF2, and the third sub-filter SF3, asdiscussed, further, above.

For example, the first filter F1 may be disposed between the antennaterminal T_ANT and the first sub-filter SF1. In such an example, one endof the first filter F1 may be connected to the antenna terminal T_ANT,and the other end of the first filter F1 may be connected to the firstsub-filter SF1. Also, an antenna ANT may be connected to the antennaterminal T_ANT.

The first filter F1 may support cellular communications in a firstfrequency band, specifically, the 3.3 GHz to 4.2 GHz band (the n77band), from among the sub-6 GHz bands. According to an example, thefirst filter F1 may support cellular communications in the 3.3 GHz to3.8 GHz band (the n78 band).

The first filter F1 may operate as a band-pass filter. For example, thefirst filter F1 may include a band-pass filter having a passband of the3.3 GHz to 4.2 GHz band. Such a band-pass filter may have a lower limitfrequency of 3.3 GHz and an upper limit frequency of 4.2 GHz. Accordingto another example, the first filter F1 may include a band-pass filterhaving a passband of the 3.3 GHz to 3.8 GHz band. In such an example,the band-pass filter has a lower limit frequency of 3.3 GHz and an upperlimit frequency of 3.8 GHz.

The first filter F1 may be composed of an LC filter. For example, the LCfilter of the first filter F1 may be implemented by using a structure ofa Chebyshev filter.

In an example, the first sub-filter SF1 may be disposed between thefirst filter F1 and a first terminal T1. In such an example, one end ofthe first sub-filter SF1 is connected to the first filter F1, and theother end of the first sub-filter SF1 is connected to the first terminalT1.

Additionally, the first sub-filter SF1 may operate as a band-stopfilter. For example, the first sub-filter SF1 may operate as a band-stopfilter having a lower limit frequency of 4.4 GHz and an upper limitfrequency of 4.6 GHz. For example, the first sub-filter SF1 may becomposed of a Surface Acoustic Wave (SAW) filter or a BAW filter havingrelatively high attenuation characteristics. However, these are onlyexamples, and other types of filters with appropriate attenuationcharacteristics may be used, as appropriate, in other examples.

Also, the first sub-filter SF1 may be disposed in a signal path betweenthe first terminal T1 and the antenna terminal T_ANT. Doing so maysufficiently ensure the attenuation characteristics of the first filterF1 for the 4.4 GHz to 5.0 GHz band (the n79 band).

According to an example, an inductor may be disposed in the signal pathbetween the first terminal T1 and the antenna terminal T_ANT. Such aninductor may provide a low-pass characteristic, so as to allow animpedance of the 4.4 GHz to 5.0 GHz band (the n79 band) to match animpedance of the 3.3 GHz to 4.2 GHz band (the n77 band), which islocated in a relatively low frequency band.

In an example, the second filter F2 may be disposed between the antennaterminal T_ANT and the second sub-filter SF2. In such an example, oneend of the second filter F2 may be connected to the antenna terminalT_ANT, and the other end of the second filter F2 may be connected to thesecond sub-filter SF2.

The second filter F2 may support cellular communications in a secondfrequency band. Specifically, the second filter F2 may support the 4.4GHz to 5.0 GHz band (the n79 band), from among the sub-6 GHz bands.

The second filter F2 may operate as a band-pass filter. For example, thesecond filter F2 may include a band-pass filter having a passband of the4.4 GHz to 5.0 GHz band. Such a filter has a lower limit frequency of4.4 GHz and an upper limit frequency of 5.0 GHz.

FIGS. 5A to 5C illustrate a process of deriving a second filteraccording to an example.

FIG. 5A illustrates an example of a circuit diagram of a Chebyshevfilter in which resonance circuits are arranged in a T-shape.

The Chebyshev filter in the example of FIG. 5A may have a predeterminedtransfer-function. The Chebyshev filter in the example of FIG. 5A mayinclude a first series resonance circuit including a first capacitor C1and a first inductor L1 connected to each other in series, a parallelresonance circuit including a second capacitor C2 and a second inductorL2 connected to each other in parallel, and a second series resonancecircuit including a third capacitor C3 and a third inductor L3 connectedto each other in series.

In such an example, the first series resonance circuit and the secondseries resonance circuit may be arranged between a first terminal Tx anda second terminal Ty. The parallel resonance circuit may be disposedbetween a ground and a node, located between the first series resonancecircuit and the second series resonance circuit.

FIG. 5B illustrates an example of a circuit diagram in which aJ-inverter technique is applied to the Chebyshev filter in the exampleof FIG. 5A.

Referring to the example of FIG. 5B, a filter in the example of FIG. 5Bmay include a capacitor 001, a capacitor C12, a capacitor C23, and acapacitor C34, where these capacitors are arranged between the terminalTx and the terminal Ty in series.

The filter in the example of FIG. 5B may include a first capacitor C1and a first inductor L1 arranged between a ground and a node, locatedbetween the capacitor C01 and the capacitor C12, and connected to eachother in parallel, a second capacitor C2 and a second inductor L2arranged between a ground and a node, located between the capacitor C12and the capacitor C23, and connected to each other in parallel, and athird capacitor C3 and a third inductor L3 arranged between a ground anda node, located between the capacitor C23 and the capacitor C34, andconnected to each other in parallel.

The filter in the example of FIG. 5B may be derived by applying aJ-inverter technique to the filter in the example of FIG. 5A.

The first capacitor C1 and the first inductor L1 connected to each otherin series, and the third capacitor C3 and the third inductor L3connected to each other in series, as illustrated in the example of FIG.5A, may be converted into a form connected in parallel, so as to bearranged between a ground and different nodes of the terminal Tx and theterminal Ty, by applying the J-inverter technique to the filter in theexample of FIG. 5A.

A capacitor 001, a capacitor C12, a capacitor C23, and a capacitor C34,having high-pass filter characteristics, may be additionally arranged tosatisfy the transfer-function of the Chebyshev filter illustrated inpart of the example of FIG. 5A.

FIGS. 6A to 6C illustrate a process of deriving a second filteraccording to an example.

FIG. 6A illustrates an example of a Chebyshev filter in which resonancecircuits are arranged in a π-shape.

The Chebyshev filter in the example of FIG. 6A may have a predeterminedtransfer-function.

The Chebyshev filter in the example of FIG. 6A may include a firstparallel resonance circuit, including a first capacitor C1 and a firstinductor L1 connected to each other in parallel, a series resonancecircuit including a second capacitor C2 and a second inductor L2connected to each other in series, and a second parallel resonancecircuit including a third capacitor C3 and a third inductor L3 connectedto each other in parallel.

The series resonance circuit may be disposed between a terminal Tx and aterminal Ty, the first parallel resonance circuit may be disposedbetween a ground and a node located between the terminal Tx and theseries resonance circuit, and the second parallel resonance circuit maybe disposed between a ground and a node located between the terminal Tyand the series resonance circuit.

FIG. 6B illustrates an example of a circuit diagram in which aK-inverter technique is applied to the Chebyshev filter in the exampleof FIG. 6A.

Referring to the example of FIG. 6B, a filter in the example of FIG. 6Bmay include a first capacitor C1 and a first inductor L1 connected toeach other in series, a second capacitor C2 and a second inductor L2connected to each other in series, and a third capacitor C3 and a thirdinductor L3 connected to each other in series, which are arrangedbetween the terminal Tx and the terminal Ty in sequence.

The filter in the example of FIG. 6B may further include an inductor L01disposed between the terminal Tx and the first capacitor C1 and thefirst inductor L1 connected in series, an inductor L12 disposed betweenthe first capacitor C1 and the first inductor L1 connected in series andthe second capacitor C2 and the second inductor L2 connected in series,an inductor L23 disposed between the second capacitor C2 and the secondinductor L2 connected in series and the third capacitor C3 and the thirdinductor L3 connected in series, and an inductor L34 disposed betweenthe terminal Ty and the third capacitor C3 and the third inductor L3connected in series.

The filter in the example of FIG. 6B may be derived by applying theK-inverter technique to the filter in the example of FIG. 6A.

The first capacitor C1 and the first inductor L1 connected to each otherin parallel, and the third capacitor C3 and the third inductor L3connected to each other in parallel, as illustrated in the example ofFIG. 6A, may be converted into a form connected in series, to bearranged between the terminal Tx and the terminal Ty, by applying theK-inverter technique to the filter in the example of FIG. 6A.

An inductor L01, an inductor L12, an inductor L23, and an inductor L34,having low-pass filter characteristics, may be additionally arranged tosatisfy the transfer-function of the Chebyshev filter, as illustrated inthe example of FIG. 6A.

FIG. 7 is a graph illustrating a frequency response of a filter to whicha J-inverter technique or a K-inverter technique is applied.

Referring to the example of FIG. 7, a first graph, or graph 1,represents a frequency response of a filter before applying a J-invertertechnique or a K-inverter technique, a second graph, or graph 2,represents a frequency response of a filter to which a J-inverter isapplied, and a third graph, or graph 3, represents a frequency responseof a filter to which a K-inverter is applied.

Referring to the examples of FIGS. 5A and 5B, and the example of FIG. 7,because of the capacitor 001, the capacitor C12, the capacitor C23, andthe capacitor C34, which may be additionally arranged in the example ofFIG. 5B, in the second graph, or graph 2, the low frequency band hasadditionally improved attenuation characteristics and the high frequencyband has additionally deteriorated attenuation characteristics, ascompared to the first graph, or graph 1.

Referring to the examples of FIGS. 6A and 6B, and the example of FIG. 7,because of the inductor L01, the inductor L12, the inductor L23, and theinductor L34, which may be additionally arranged as in the example ofFIG. 6B, in the third graph, or graph 3, the high frequency band hasfurther improved attenuation characteristics and the low frequency bandhas further deteriorated attenuation characteristics, as compared to thefirst graph, or graph 1.

Therefore, it is required to improve the attenuation characteristicsthat would otherwise deteriorate in the high frequency band by includingthe capacitor 001, the capacitor C12, the capacitor C23, and thecapacitor C34 as in the example of FIG. 5B, and the attenuationcharacteristics that would otherwise deteriorate in the low frequencyband by the inductor L01, the inductor L12, the inductor L23, and theinductor L34 as in the example of FIG. 6B.

FIG. 5C is a circuit diagram illustrating a second filter F2 accordingto an example.

The second filter F2 according to an example in the example of FIG. 5Cmay further include an inductor L21, an inductor L22, and an inductorL23, as compared to the filter in the example FIG. 5B.

Referring to the example of FIG. 5C, the second filter F2 according toan example may include a first parallel LC resonance circuit, a secondparallel LC resonance circuit, a third parallel LC resonance circuit,the inductor L21, the inductor L22, the inductor L23, a capacitor C01, acapacitor C12, a capacitor C23, and a capacitor C34.

In such an example, the first parallel LC resonance circuit may includea first capacitor C1 and a first inductor L1 connected to each other inparallel, the second parallel LC resonance circuit may include a secondcapacitor C2 and a second inductor L2 connected to each other inparallel, and the third parallel LC resonance circuit may include athird capacitor C3 and a third inductor L3 connected to each other inparallel.

The first parallel LC resonance circuit, the second parallel LCresonance circuit, and the third parallel LC resonance circuit may bedisposed between a ground and different nodes, from among a plurality ofnodes between a first terminal Tx and a second terminal Ty. Thus, eachof the first parallel LC resonance circuit, the second parallel LCresonance circuit, and the third parallel LC resonance circuit may bedisposed between a ground and a node of different nodes located betweenthe capacitor 001, the capacitor C12, the capacitor C23, and thecapacitor C34.

Also, the inductor L21 may be disposed between the first parallel LCresonance circuit and a ground, the inductor L22 may be disposed betweenthe second parallel LC resonance circuit and a ground, and the inductorL23 may be disposed between the third parallel LC resonance circuit anda ground.

In the example of FIG. 5C, although an inductor is illustrated as beingconnected to each of the first parallel LC resonance circuit, the secondparallel LC resonance circuit, and the third parallel LC resonancecircuit, the inductor may be connected to only one parallel LC resonancecircuit selected from among the first parallel LC resonance circuit, thesecond parallel LC resonance circuit, and the third parallel LCresonance circuit, according to an example. Further, according to anexample, two parallel LC resonance circuits among the first parallel LCresonance circuit, the second parallel LC resonance circuit, and thethird parallel LC resonance circuit may be connected to a ground via asingle inductor.

The inductor L21, the inductor L22, and the inductor L23, respectivelyconnected to the first parallel LC resonance circuit, the secondparallel LC resonance circuit, and the third parallel LC resonancecircuit, may form an additional attenuation region, to improve theattenuation characteristics deteriorated in the high frequency band,because of the capacitor C01, the capacitor C12, the capacitor C23, andthe capacitor C34, which may be additionally disposed at the time ofapplying the J-inverter technique.

The second filter F2 may secure sufficient attenuation characteristicsfor the 5.15 GHz to 5.95 GHz band (the 5 GHz Wi-Fi band) by anattenuation region formed by the presence of inductor L21, the inductorL22, and the inductor L23.

FIG. 6C is a circuit diagram illustrating a second filter F2 accordingto another example.

Referring to FIG. 6C, the second filter F2 according to an embodiment inFIG. 6C may further include a capacitor Cz1, a capacitor Cz2, and acapacitor Cz3, in addition to the second filter F2 according to anembodiment in FIG. 6B.

Referring to the example of FIG. 6C, the second filter F2 according toan example may include a first series LC resonance circuit, a secondseries LC resonance circuit, a third series LC resonance circuit, thecapacitor Cz1, the capacitor Cz2, the capacitor Cz3, an inductor L01, aninductor L12, an inductor L23, and an inductor L34.

For example, the first series LC resonance circuit may include a firstcapacitor C1 and a first inductor L1 connected to each other in series,the second series LC resonance circuit may include a second capacitor C2and a second inductor L2 connected to each other in series, and thethird series LC resonance circuit may include a third capacitor C3 and athird inductor L3 connected to each other in series.

The first series LC resonance circuit, the second series LC resonancecircuit, and the third series LC resonance circuit may be arrangedbetween a first terminal Tx and a second terminal Ty. Also, the firstseries LC resonance circuit, the second series LC resonance circuit, andthe third series LC resonance circuit may be arranged between theinductor L01, the inductor L12, the inductor L23, and the inductor L34.

The capacitor Cz1 may be connected to the first series LC resonancecircuit in parallel, the capacitor Cz2 may be connected to the secondseries LC resonance circuit in parallel, and the capacitor Cz3 may beconnected to the third series LC resonance circuit in parallel.

In the example of FIG. 6C, although a capacitor is illustrated as beingconnected to each of the first series LC resonance circuit, the secondseries LC resonance circuit, and the third series LC resonance circuit,in other examples, the capacitor may be connected to only one series LCresonance circuit selected from among the first series LC resonancecircuit, the second series LC resonance circuit, and the third series LCresonance circuit, according to an example. The capacitor Cz1, thecapacitor Cz2, and the capacitor Cz3, respectively connected to thefirst series LC resonance circuit, the second series LC resonancecircuit, and the third series LC resonance circuit, may form anadditional attenuation region, to improve the attenuationcharacteristics otherwise deteriorated in the low frequency band, by thepresence of the inductor L01, the inductor L12, the inductor L23, andthe inductor L34.

The second filter F2 may secure sufficient attenuation characteristicsfor the 3.3 GHz to 4.2 GHz band (the n77 band) by including anattenuation region formed by the presence of the capacitor Cz1, thecapacitor Cz2, and the capacitor Cz3.

Referring again to the example of FIG. 4A, the second sub-filter SF2 maybe disposed between the second filter F2 and a second terminal T2. Oneend of the second sub-filter SF2 may be connected to the second filterF2, and the other end of the second sub-filter SF2 may be connected tothe second terminal T2.

For example, the second sub-filter SF2 may act as a band-stop filter.The second sub-filter SF2 may be composed of a SAW filter or a BAWfilter having relatively high attenuation characteristics. The secondsub-filter SF2 may be disposed in a signal path between the secondterminal T2 and the antenna terminal T_ANT, in order to compensate forthe attenuation characteristics of the second filter F2.

For example, when the second filter F2 is configured according to anexample as per FIG. 5C, the second sub-filter SF2 may include a bandstop filter having a stop band of a 4.0 GHz to 4.2 GHz band. Forexample, such a filter may have a lower frequency of 4.0 GHz, and anupper limit frequency of 4.2 GHz. The second sub-filter SF2 maysufficiently compensate for the attenuation characteristics of thesecond filter F2 for the 3.3 GHz to 4.2 GHz band (the n77 band).Therefore, the second filter F2 according to an example as per FIG. 5Cmay secure sufficient attenuation characteristics for a 5.15 GHz to 5.95GHz band by an attenuation region formed by the inductor L21, theinductor L22, and the inductor L23, and may secure sufficientattenuation characteristics for the 3.3 GHz to 4.2 GHz band (the n77band) by using the stop band of the 4.0 GHz to 4.2 GHz band of thesecond sub-filter SF2.

As another example, when the second filter F2 is configured according toan example as per FIG. 6C, the second sub-filter SF2 may include a bandstop filter having a stop band of a 5.15 GHz to 5.35 GHz band. Here, thesecond sub-filter SF2 has a lower frequency of 5.15 GHz, and an upperlimit frequency of 5.35 GHz. Thus, the second sub-filter SF2 maysufficiently compensate for the attenuation characteristics of thesecond filter F2 with respect to the 5.15 GHz to 5.95 GHz band (the 5GHz Wi-Fi band).

As a result, the second filter F2 according to the example of FIG. 6Cmay secure sufficient attenuation characteristics for the 3.3 GHz to 4.2GHz band (the n77 band) by using an attenuation region formed by thecapacitor Cz1, the capacitor Cz2, and the capacitor Cz3. The secondfilter F2 may secure sufficient attenuation characteristics for the 5.15GHz to 5.95 GHz band (the 5 GHz Wi-Fi band) by using the stop band ofthe 5.15 GHz to 5.35 GHz band of the second sub-filter SF2.

According to an example, the second filter F2 may be configured asillustrated in the examples of FIG. 5C and FIG. 6C, in order to reducethe number of band stop filters, used for providing the attenuationcharacteristics for neighboring bands, to one.

The third filter F3 may be disposed between the antenna terminal T_ANTand the third sub-filter SF3. One end of the third filter F3 may beconnected to the antenna terminal T_ANT, and the other end of the thirdfilter F3 may be connected to the third sub-filter SF3.

The third filter F3 may support Wi-Fi communications in the thirdfrequency band, specifically, the 5 GHz band. As an example, the thirdfilter F3 may support Wi-Fi communications in the 5.15 GHz to 5.95 GHzband.

In such an example, the third filter F3 may operate as a band-passfilter. For example, the third filter F3 may include a band-pass filterhaving a passband of the 5.15 GHz to 5.95 GHz band. Such a third filterF3 may have a lower limit frequency of 5.15 GHz and an upper limitfrequency of 5.95 GHz.

The third filter F3 may also be composed of an LC filter. For example,the LC filter of the third filter F3 may be implemented by using astructure of a Chebyshev filter.

The third sub-filter SF3 may be disposed between the third filter F3 anda third terminal T3. One end of the third sub-filter SF3 may beconnected to the third filter F3. The other end of the third filter F3may be connected to the third terminal T3.

The third sub-filter SF3 may operate as a band-stop filter. For example,the third sub-filter SF3 may operate as a band-stop filter having alower limit frequency of 4.8 GHz and an upper limit frequency of 5.0GHz. Such a third sub-filter SF3 may be composed of a SAW filter or aBAW filter having relatively high attenuation characteristics, asdiscussed further, above.

The third sub-filter SF3 may be disposed in a signal path between thethird terminal T3 and the antenna terminal T_ANT. Doing so ensuressufficient attenuation characteristics for the third filter F3 withrespect to the 4.4 GHz to 5.0 GHz band. According to an example, acapacitor may be disposed in the signal path between the third terminalT3 and the antenna terminal T_ANT. Such a capacitor may provide ahigh-pass characteristic, which allows an impedance of the 4.4 GHz to5.0 GHz band (the n79 band) to match an impedance of the 5.15 GHz to5.95 GHz band (the Wi-Fi 5 GHz band), which is located in a relativelyhigh frequency band.

FIG. 8 illustrates frequency responses by first to third filtersaccording to an example. FIG. 9 illustrates frequency responses by firstto third filters and first to third sub-filters according to an example.

Referring to the example of FIG. 8, even when first to third filters areimplemented by using a Chebyshev filter, such that a passband has arelatively broad bandwidth of 600 MHz or more, excellent insertion losscharacteristics and reflection loss characteristics may still berealized.

Referring to the example of FIG. 9, each of first to third sub-filtersmay be connected to each first to third filters, such that the 3.3 GHzto 4.2 GHz band (the n77 band), the 4.4 GHz to 5.0 GHz band (the n79band), and the 5.15 GHz to 5.95 GHz band (the 5 GHz Wi-Fi band) maysecure sufficient attenuation characteristics with respect to eachother.

FIG. 10 is a block diagram illustrating an example of an amplifierconnected to a filter according to an example.

In the example of FIG. 10, it may be understood that a filter F maycorrespond to any one of the first filter F1, the second filter F2, andthe third filter F3 of the example of FIG. 4A, or may correspond to anyone of the sub-filter SF1, the second sub-filter SF2, and the thirdsub-filter SF3 of the example of FIG. 4B. It may also be understood thata receiving terminal Rx and a transmitting terminal Tx may be includedin any one of a first terminal T1 to a fourth terminal T4 according tovarious examples. For example, the first terminal T1 may include thereceiving terminal Rx and the transmitting terminal Tx.

Additionally, an amplifying unit AU may include a switch SW, a low noiseamplifier LNA, and a power amplifier PA.

Referring to the example of FIG. 10, the filter F may be connected toone end of the low noise amplifier LNA and one end of the poweramplifier PA through the switch SW. The low noise amplifier LNA may bedisposed in a receiving path (Rx_RF) of an RF signal. Accordingly, thepower amplifier PA may be disposed in a transmission path (Tx_RF) of theRF signal. The other end of the low noise amplifier LNA may be connectedto the receiving terminal Rx, and the other end of the power amplifierPA may be connected to the transmitting terminal Tx.

In the example of FIG. 10, an example is illustrated in which the lownoise amplifier LNA is disposed in the receiving path Rx_RF, and thepower amplifier PA is disposed in the transmission path Tx_RF. Dependingon the necessity of amplification according to the design of an example,the low noise amplifier LNA may be removed from the receiving pathRx_RF, or the power amplifier PA may be removed from the transmissionpath Tx_RF.

According to an example, the number of antennas employed in a mobiledevice may be reduced to improve the isolation characteristic of theantenna.

According to an example, sufficient attenuation characteristics forneighboring bands may be ensured.

While this disclosure includes specific examples, it will be apparentafter an understanding of the disclosure of this application thatvarious changes in form and details may be made in these exampleswithout departing from the spirit and scope of the claims and theirequivalents. The examples described herein are to be considered in adescriptive sense only, and not for purposes of limitation. Descriptionsof features or aspects in each example are to be considered as beingapplicable to similar features or aspects in other examples. Suitableresults may be achieved if the described techniques are performed in adifferent order, and/or if components in a described system,architecture, device, or circuit are combined in a different manner,and/or replaced or supplemented by other components or theirequivalents. Therefore, the scope of the disclosure is defined not bythe detailed description, but by the claims and their equivalents, andall variations within the scope of the claims and their equivalents areto be construed as being included in the disclosure.

What is claimed is:
 1. A frontend module, comprising: a first filterhaving a passband of a first frequency band; a second filter having apassband of a second frequency band, the second frequency band beinghigher than the first frequency band; a third filter having a passbandof a third frequency band, the third frequency band being higher thanthe second frequency band; and a sub-filter, connected to the secondfilter, configured to provide attenuation characteristics for the firstfrequency band, wherein the second filter comprises a plurality ofparallel LC resonance circuits arranged between a ground and differentnodes, from among a plurality of nodes between a first terminal and asecond terminal, wherein an inductor is connected to a portion of theplurality of parallel LC resonance circuits, and wherein the firstfrequency band is a band of 3.3 GHz to 4.2 GHz, the second frequencyband is a band of 4.4 GHz to 5.0 GHz, and the third frequency band is aband of 5.15 GHz to 5.95 GHz.
 2. The frontend module of claim 1, whereinthe inductor is configured to provide attenuation characteristics forthe third frequency band.
 3. The frontend module of claim 1, wherein theinductor is disposed between the portion of the plurality of parallel LCresonance circuits, and the ground.
 4. The frontend module of claim 1,wherein the second filter comprises a plurality of inductors, and eachof the plurality of inductors is connected to a different parallel LCresonance circuit of the plurality of parallel LC resonance circuits. 5.The frontend module of claim 1, wherein the second filter comprises aplurality of capacitors, and each of the plurality of parallel LCresonance circuits is arranged between a ground and a different nodebetween the plurality of capacitors.
 6. The frontend module of claim 1,wherein the first filter, the second filter, and the third filter areconnected to an antenna terminal.
 7. The frontend module of claim 1,wherein the sub-filter has a stop band of 4.0 GHz to 4.2 GHz.
 8. Afrontend module, comprising: a first filter having a passband of a firstfrequency band; a second filter having a passband of a second frequencyband, the second frequency band being higher than the first frequencyband; a third filter having a passband of a third frequency band, thethird frequency band being higher than the second frequency band; and asub-filter, connected to the second filter, configured to provideattenuation characteristics for the first frequency band, wherein thesecond filter comprises a plurality of series LC resonance circuitsarranged between a first terminal and a second terminal, wherein acapacitor is connected to a portion of the plurality of series LCresonance circuits, and wherein the first frequency band is a band of3.3 GHz to 4.2 GHz, the second frequency band is a band of 4.4 GHz to5.0 GHz, and the third frequency band is a band of 5.15 GHz to 5.95 GHz.9. The frontend module of claim 8, wherein the first filter, the secondfilter, and the third filter are connected to an antenna terminal. 10.The frontend module of claim 8, wherein the capacitor is configured toprovide attenuation characteristics for the first frequency band. 11.The frontend module of claim 8, wherein the capacitor is connected tothe portion of the plurality of series LC resonance circuits inparallel.
 12. The frontend module of claim 8, wherein the second filtercomprises a plurality of capacitors, and each of the plurality ofcapacitors is connected to a different series LC resonance circuits ofthe plurality of series LC resonance circuits.
 13. The frontend moduleof claim 8, wherein the second filter comprises a plurality ofinductors, and each of the plurality of series LC resonance circuits isdisposed between the plurality of inductors.
 14. The frontend module ofclaim 8, wherein the sub-filter has a stop band of 5.15 GHz to 5.35 GHz.